Wireless communication systems have been widely deployed to provide various types of communication services such as voice or data. In general, a wireless communication system is a multiple access system that supports communication with multiple users by sharing available system resources (bandwidth, transmission power, etc.). For example, multiple access systems include a code division multiple access (CDMA) system, a frequency division multiple access (FDMA) system, a time division multiple access (TDMA) system, an orthogonal frequency division multiple access (OFDMA) system, a single carrier frequency division multiple access (SC-FDMA) system, and a multi-carrier frequency division multiple access (MC-FDMA) system.
Along with advances in information communication technology, various wireless communication techniques have been developed. Thereamong, a wireless local area network (WLAN) enables users to wirelessly access the Internet through portable terminals such as personal digital assistants (PDAs), laptops, and portable multimedia players (PMPs) in homes, offices, or specific service areas, based on wireless frequency technology.